A semiconductor device in which a Zener diode is arranged between an outside terminal and GND is disclosed in, for example, JP 7-147727 A. The Zener diode is used to protect a circuit from destruction caused by electro static discharge (ESD) and noise such as surge.
FIGS. 5A and 5B are schematic views showing the semiconductor in which the Zener diode is arranged between the outside terminal and GND. FIG. 5A is a schematic view showing an equivalent circuit around the outside terminals t1 and t2 in the semiconductor device 90, and FIG. 5B is schematic top view showing arrangement of circuit elements in a semiconductor chip 90c. 
In FIG. 5A, the outside terminals t1 and t2 are respectively a power terminal and an output terminal. The semiconductor device 90 includes Zener diodes Z1 and Z2, each of which includes three diodes connected in series, connected between the outside terminals t1 and t2 and GND to bypass a noise current such as ESD and surge.
As shown in FIG. 5B, the semiconductor device connects the Zener diodes Z1 and Z2 near the outside terminals t1 and t2 and a GND terminal g by a short wire to bypass the noise current to GND as soon as possible.
Recently, Zener diodes Z1 and Z2 having high noise tolerance are desirable. However, if the size of the Zener diodes Z1 and Z2 becomes larger in order to have the high noise tolerance, the semiconductor itself also becomes larger, and production costs rise.